1. Field of the Invention
The present invention relates to a moving body drive apparatus for automatically opening and closing a moving body such as a door of a vehicle.
2. Description of the Related Art
In a door opening and closing apparatus for a vehicle (called a “moving body drive apparatus” below), a device using a rack and pinion is a highly reliable system which causes few breakdowns and hardly requires any maintenance.
For example, in the case of a single sliding door for a railway carriage, or a double sliding door for same in which one door panel is opened and closed by a single moving body drive apparatus, a single rack having a length adjusted to approximately the full opening and closing length of the door is used in a door apparatus which uses a rotary motor. If this rack is formed into a sealed structure, then the length of the case of the moving body drive apparatus cannot be made shorter than two times the full opening and closing length of the door, due to the amount of movement of the rack.
FIGS. 7A and 7B and FIGS. 8A and 8B are schematic drawings of a conventional door apparatus 100 based on a moving body drive apparatus using a rack and pinion. In this moving body drive apparatus, a pinion fixed to a motor shaft is rotated in a corresponding direction, by rotation of the motor in either a forward or reverse direction, and a rack, which is installed so as to be engaged with the pinion, moves accordingly in either a leftward or rightward direction. A door is attached to the rack, and the door is opened and closed corresponding to the leftward and rightward movement of the rack.
FIGS. 7A and 7B are diagrams showing a door in a fully open state, and FIGS. 8A and 8B are diagrams showing a door in a fully closed state. FIGS. 7A and 7B are respectively a front surface diagram and an upper surface diagram of the door apparatus 100 in a fully open state of the door. FIGS. 8A and 8B are respectively a front surface diagram and an upper surface diagram of the door apparatus 100 in a fully closed state.
The operation of the respective parts is now described with reference to FIG. 7A. The door apparatus 100 includes a door panel 102, a moving body drive apparatus to drive the door panel 102, a housing case 104, and a door rail 106 for guiding the door panel 102, and the like.
The moving body drive apparatus includes a drive motor (not illustrated), a pinion 114, a rack 116, a drive arm 108, and the like. The pinion 114 is fixed to one end of the output shaft of the drive motor, and is accommodated inside the housing case 104 together with a rack 116 which engages with the pinion 114. The pinion 114 is disposed near a central position of the housing case 104, in the opening and closing direction.
The rack 116 is a member which is long in the lateral direction and has a gear for engaging with the pinion 114 formed in an upper portion thereof. The rack 116 is provided movably in the opening and closing direction, by a rail, or the like, which is not illustrated. A drive arm 108 to drive the door panel 102 is provided downward on the bottom portion of the right end side of the rack 116. The door rail 106 is provided in the lower portion of the housing case 104 and has virtually the same total length as the housing case 104.
Door hangers 112 are provided on the left and right ends of the door panel 102. The door panel 102 is suspended movably on the door rail 106 via the left and right door hangers 112. Rollers 118 inserted smoothly into a rail groove 106a formed in the lower end portion of the door rail 106 and guiding the opening and closing movement of the door panel 102 are installed on the door hangers 112. A door coupling section 110 is provided in the right end upper section of the door panel 102 and a drive arm 108 is coupled with this door coupling section 110.
In this structure, when the pinion 114 is rotated in a counter-clockwise direction in the drawings, from the position in the open state shown in FIG. 7A, the rack 116 moves rightward and the door panel 102 which is coupled with the rack 116 via the drive arm 108 and the door coupling section 110 is moved to the position of the closed state shown in FIG. 8A.
As the rack 116 moves from the open position of the door panel 102 to the closed position, the rack 116 moves from the position shown in FIG. 7B to the position shown in FIG. 8B. A space approximately two times the length of the rack is required in the door apparatus 100, in order for the rack 116 to be able to move through approximately two times the length thereof (which corresponds to the amount of movement of the door panel). Furthermore, in order to hermetically seal the rack 116, the housing case 104 is also required to have a length approximately two times the length of the rack.
On the other hand, there is a requirement to make the door apparatus compact in size in order to make the vehicle compact and ensure the internal space, and in particular, it is necessary to shorten the length of the door apparatus in the opening and closing direction thereof. As one proposal for shortening the length of the moving body drive apparatus in the opening and closing direction, Japanese Patent Application Publication No. 2010-196254 proposes a moving body drive apparatus which shortens the length of the door apparatus in the opening and closing direction, by disposing two pinions at a prescribed distance apart and engaging the two pinions with a rack.
FIG. 9 is a diagram showing a concrete example of the moving body drive apparatus proposed in Japanese Patent Application Publication No. 2010-196254. FIG. 9 shows a state where the door is in a right-side position and is closed. A second pinion 114b is provided at a position separated by a prescribed distance from a first pinion 114a which is installed on the drive shaft of a motor 120.
An upper rack 116a and a lower rack 116b are respectively provided movably in the left/right direction, on the upper side and the lower side of the housing case. A door panel is coupled to the lower rack 116b. The upper rack 116a is a relay rack for transmitting drive force from the first pinion 114a, to the second pinion 114b. One of the upper rack 116a and the lower rack 116b is provided so as to be engaged with the first pinion 114a at all times.
In a state where the door as shown in FIG. 9 has been opened half-way from the fully closed state, the upper rack 116a is engaged with both the first pinion 114a and the second pinion 114b, and the lower rack 116b is moved leftwards due to engagement with the second pinion 114b. When the lower rack 116b moves leftwards and has moved more than half-way to the left, then the engagement between the upper rack 116a and the first pinion 114a is released, the lower rack 116b is engaged directly with the first pinion 114a, and the lower rack 116b moves to a fully open state.
In a method based on a relationship in which the door moves through a distance corresponding to the length of the rack as in Japanese Patent Application Publication No. 2010-196254 shown in FIG. 9, supposing that the door moves through a distance corresponding to the width of the door, then the total length of the moving body drive apparatus will be approximately two times the length of the rack. In the example shown in FIG. 9, the total length W1 of the portion corresponding to the moving body drive apparatus is approximately two times the total opening and closing width W0. Since the opening and closing length of the vehicle door often exceeds 1 meter at present, the total length of the portion corresponding to the moving body drive apparatus is 2 meters or greater.
In a moving body drive apparatus having an enlarged size, there is no spare margin in the length direction of the head jamb, for instance, in an end door of a railway carriage, and therefore outfitting and layout are difficult to carry out. Therefore, the size of the structure, such as the vehicle is limited. Furthermore, if both ends of the rack are moved to a distance of two times the opening and closing distance of the whole door, then caution is also required in respect of interference between the attachment section of the vehicle, etc. and the rack after installation. As described above, from the viewpoint of the freedom of layout inside the vehicle and saving space, etc., there is a requirement to shorten the length of the moving body drive apparatus in the direction of movement.